D-Net

package eu.dnetlib.parthenos.virtuoso;

import java.io.OutputStream;

import java.util.Iterator;

import java.util.List;

import com.google.common.collect.Iterators;

import com.google.common.collect.Lists;

import org.apache.commons.logging.Log;

import org.apache.commons.logging.LogFactory;

import org.apache.jena.query.Query;

import org.apache.jena.query.QueryExecutionFactory;

import org.apache.jena.query.QueryFactory;

import org.apache.jena.query.ResultSet;

import org.apache.jena.rdf.model.Model;

import org.apache.jena.riot.RDFDataMgr;

import org.apache.jena.riot.RDFFormat;

import org.apache.jena.sparql.engine.http.QueryEngineHTTP;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.RequestParam;

import org.springframework.web.bind.annotation.RestController;

import virtuoso.jena.driver.VirtGraph;

import virtuoso.jena.driver.VirtuosoQueryExecution;

import virtuoso.jena.driver.VirtuosoQueryExecutionFactory;

/**

 * Created by Alessia Bardi on 31/01/2018.

 * Read-only API for virtuoso.

 *

 * //TODO: pagination

 * //TODO swagger documentation?

 *

 * @author Alessia Bardi

 */

@RestController

public class VirtuosoReadAPI {

	private static final Log log = LogFactory.getLog(VirtuosoReadAPI.class);

	@Value("${virtuoso.sparqlurl}")

	private String sparqlUrl;

	@Value("${virtuoso.pwd}")

	private String username;

	@Value("${virtuoso.pwd}")

	private String password;

	@Value("${virtuoso.uri.base.default}")

	private String defaultBaseURI;

	@RequestMapping(value = "/virtuoso/graphs", produces = { "application/json" }, method = RequestMethod.GET)

	public List<String> getGraphURLs(@RequestParam final String api) {

		String queryForGraphs =

				"SELECT DISTINCT ?g WHERE { { ?g <dnetcollectedFrom> <"+defaultBaseURI+api+"> }}";

		log.debug(queryForGraphs);

		Query query = QueryFactory.create(queryForGraphs);

		final QueryEngineHTTP serviceRequest = QueryExecutionFactory.createServiceRequest(sparqlUrl, query);

		ResultSet graphs = serviceRequest.execSelect();

		Iterator<String> s = Iterators.transform(graphs, qs -> qs.getResource("g").getURI());

		List<String> res = Lists.newArrayList(s);

		serviceRequest.close();

		return res;

	}

	@RequestMapping(value = "/virtuoso/subjects", produces = { "application/json" }, method = RequestMethod.GET)

	public List<String> getSubjectsForGraph(@RequestParam final String graph) {

		// To filter out all subjects that do not start with 'http' use the following query

		// String queryForSubjectsTemplate = "SELECT DISTINCT ?s WHERE {GRAPH <%s> {?s ?p ?o . FILTER regex(str(?s),'^http')}}";

		// Based on FORTH observation, those without a URL should not be interesting by themselves, but looking at Nakala data it seems this is not the case:

		String queryForSubjectsTemplate = "SELECT DISTINCT ?s WHERE {GRAPH <%s> {?s ?p ?o }}";

		String q = String.format(queryForSubjectsTemplate, graph);

		log.debug(q);

		final QueryEngineHTTP serviceRequest =

				QueryExecutionFactory.createServiceRequest(sparqlUrl, QueryFactory.create(q));

		ResultSet subjects = serviceRequest.execSelect();

		Iterator<String> s = Iterators.transform(subjects, qs -> qs.getResource("s").getURI());

		List<String> res = Lists.newArrayList(s);

		serviceRequest.close();

		return res;

	}

	@RequestMapping(value = "/virtuoso/subject", produces = { "application/rdf+xml", "application/xml" }, method = RequestMethod.GET)

	public void getSubject(@RequestParam final String subjectURL, final OutputStream responseStream) {

		//String describeQuery = "DESCRIBE <" + subjectURL + ">";

		//log.debug(describeQuery);

		//Can't use DESCRIBE query: server decides what to return (i.e. not all triples) and cannot find out if and how Virtuoso can be configured

		String q = "DEFINE input:inference <parthenos_rules> CONSTRUCT {<%s> ?p ?o . } WHERE { <%s> ?p ?o .}";

		//String q = "CONSTRUCT {<%s> ?p ?o . } WHERE { <%s> ?p ?o .}";

		String query = String.format(q, subjectURL, subjectURL, subjectURL, subjectURL);

		log.debug(query);

		VirtGraph g = new VirtGraph(sparqlUrl, username, password);

		g.setReadFromAllGraphs(true);

		VirtuosoQueryExecution vqe = VirtuosoQueryExecutionFactory.create(query, g);

		Model resultModel = vqe.execConstruct();

		RDFDataMgr.write(responseStream, resultModel, RDFFormat.RDFXML_PLAIN);

		vqe.close();

		g.close();

	}

}